Recent studies have indicated that normal rats have an intrinsic asymmetry in nigrostriatal function. The asymmetry appears to be related to spatial behavior. Dopamine levels are lower in the striata ipsilateral to rats' side preferences than in the striata contralateral to rats' side preferences. Amphetamine potentiates the striatal dopamine asymmetry and induces circling behavior (rotation) toward the side with the lower level of dopamine. The proposed experiments are designed to provide a detailed functional analysis of cerebral asymmetry in the rat. The behavioral effects of unilateral brain lesions will be examined in terms of whether such effects vary with the side of the lesion. The neurochemical and neuroanatomical specificity of the dopamine asymmetry will be determined and the role of interhemispheric pathways in maintaining a behavioral and/or neurochemical asymmetry will be studied. The results of the proposed studies may, eventually, be helpful in explaining some aspects of the etiology and symptomatology of particular neurological syndromes (e.g. Parkinson's Disease) in which cerebral dominance is affected.